Method and apparatus for producing filament reinforced tubular products on a continuous basis

ABSTRACT

A device for making filament reinforced tubular products in a continuous manner. The device includes a series of filament spools. Filament from the spools is passed through a resin tank and around a fixed mandrel to form the longitudinal strands of the tube. The mandrel has substantially the same internal size and shape of the continuous tube to be produced. The mandrel extends through a plurality of helical filament wrap devices which are designed to apply opposing helically wound strands of filament upon the longitudinal strands. The mandrel extends also through a pair of circumferential filament wrap devices for laying outermost surface circumferential strands in opposite directions with respect to each other and superimposed upon the helical immediately preceding final strands. The several layers of such strands which have been wound on the fixed mandrel are urged into a dielectric curing zone which is also located to receive the terminal end of the mandrel. After the resin matrix has been cured, the finally formed and cured tube is pulled from the mandrel by a pulling unit. A number of embodiments are disclosed for making continuously wound pipe. In another embodiment, the device is mounted on a moving vehicle such as a boat where continuously made pipe is deposited from the moving vehicle. In an additional embodiment of the invention, a rectangular mandrel is employed for wrapping tube-like sections having a somewhat rectangular cross section, capable of being used in the construction of ladder rails and similar structural elements.

Mite States Patent 1 Goldsworthy et a1.

[ METHOD AND APPARATUS FOR PRGDUCING FHLAMENT REINFORCED TUBULARPRODUCTS ON A CONTINUOUS BASlS [75] Inventors: William B. Goldsworthy,Palos Verdes Estates; Ethridge E. Hardesty, Pine Valley,'both of Calif.

[73] Assignee: GoldsworthyEngineering, 1nc.,

Torrance, Calif.

[22] Filed: Mar. 18, 1971 .[21] Appl. No.: 125,774

Related U.S. Application Data [63] Continuation-in-part of Ser. No.723,554, April 23, 1968, Pat. No. 3,579,402, which is acontinuation-in-part of Ser. No. 633,146, April 24, 1967, abandoned.

[52] U.S. Cl 156/172, 156/173,156/175, 156/180, 156/203, 156/244,156/273, 156/275, 156/425, 156/430, 156/432 [51] Int. Cl. B3lc 3/00 [58]Field of Search 156/431, 432, 244, 156/392, 425, 173, 272, 274, 446,143; 6/72.2, 72.3

[56] References Cited UNITED STATES PATENTS 2,723,705 11/1955 Collins156/432 X 2,863,204 12/1958 Timothy et a1. 156/392 X 3,399,094 8/1968Skoggard et a1. 156/244 X 3,138,511 6/1964 Cadwallader 156/431 3,108,92110/1963 Gillman et al. 156/432 3,532,579 10/1970 Havens et al. 156/4313,306,797 2/1967 Boggs 156/432 3,470,051 9/1969 Meyer... 156/244 X3,503,828 3/1970 Walter 156/382 FOREIGN PATENTS OR APPLICATIONS 569,75611/1957 Italy 156/432 1 Oct. 30, 1973 Primary Examiner-Alfred L. LeavittAssistant ExaminerDavid A. Simmons Attorney-Robert J. Schaap, John D.Upham and Joseph D. Kennedy 57 ABSTRACT A device for making filamentreinforced tubular products'in a continuous manner. The device includesa series of filament spools. Filament from the spools is passed througha resin tank and around a fixed mandrel to form the longitudinal strandsof the tube. The mandrel has substantially the same internal size andshape of the continuous tube to be produced. The mandrel extends througha plurality of helical filament wrap devices which are designed to applyopposing helically wound strands of filament upon the longitudinalstrands. The mandrel extends also through a pair of circumferentialfilament wrap devices for laying outermost surface circumferentialstrands in opposite directions with respect to each other andsuperimposed upon the helical immediately preceding final strands. Theseveral layers of such strands which have been wound on the fixedmandrel are urged into a dielectric curing zone which is also located toreceive the terminal end of the. mandrel. After the resin matrix hasbeen cured, the finally formed and cured tube is pulled from the mandrelby a pulling unit.

A-number of embodiments are disclosed for making continuously woundpipe. In another embodiment, the

, device is mounted on-a moving vehicle such as a boat 26 Claims, 40Drawing Figures PAIENIEU [1m 30 i973 SHEET 010! 12 INVENTORS WILLIAM B.GOLDSWORTHY ETHRIDGE E. HARDESTY ATTORNEY mmgnomso ms (3.769.127 sum 020F 12 "III,"

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INVENTORS WILLIAM B. GOLDSWORTHY YETHRIDCSE E. HARDESTY B MWLQJCW AT TORNEY PATENTED UN 30 I975 SHEET IEUF 12 FIG INVENTORS WILLIAM B-GOLDSWORTHY ETHRIDGE E. HARDESTY 'ATTORNEY METHOD AND APPARATUS FORPRODUCING FILAMENT REINFORCED TUBULAR PRODUCTS ON A CONTINUOUS BASISThis application is a continuation-in-part of copending application Ser.No. 723,554, filed Apr. 23, 1968, now U.S. Pat. No. 3,579,402, and whichis in turn a continuation-in-part of copending application Ser. No.633,146, filed Apr. 24, 1967, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to certain new anduseful improvements in apparatus and method for making a filamentreinforced tube, and more particularly, man improved apparatus andmethod for forming filament reinforced tubing on a continuous basis andwhich tubing can be used as fluid piping having high performancecharacteristics. This tubing is also highly effective in the making ofstructural elements or in use in any other environment where tubularmembers are normally employed.

The use, acceptance and reliability of tube and pipe products formed ofmaterials other than metal is rapidly growing. Extruded thermoplasticpipe is being widely employed for service water systems, sprinklersystems and the like. Furthermore, where the thermoplastic resin used inthe making of these non-metal pipes hasthe suitable characteristics, thepipes can be used in the transportation of chemical and waste fluidswhere metal may be subjected to severe chemical attack and corrosion.Extruded thermoplastic pipe is, however, limited in its ability tocontain pressure. Long-run pipe lines must operate at a relatively highpressure. Similarly, domestic service pipe lines which are required toserve locations on hills and mountains must also operate at highpressure. Throughout the chemical industry in particular, fluids aretransported in pipe at elevated pressures.

Until recently, only metal pipe was able to withstand liquid workingpressures above approximately one hundred pounds per square inch' in aoneinch diameter pipe. Normally, tap water of the type delivered toconsumers is corrosive to metal pipe dependent upon the chemicalconstituents of the water. Furthermore, most chemicals will attack metalpipe, and sometimes, these reactions may be quite violent anddestructive. In order to obviate this corrosion problem, small diameterpipes which were used for conducting fluids at relatively low pressurewere made from copper. Pipes with larger diameters were made from steeland stainless steel, but all types required periodic replacement.Furthermore,

many of the steel pipes incorporated protective inner-.

linings made from ceramics and thermoplastic materials, rubber, etc.However, the pipe-to-pipe connecting joints were vulnerable since thepipe lining protected only the internal annular wall of the pipe fromcorrosion and not the connecting joint. The methods for bridging thesejoints are generally expensive and oftentimes dangerous as well.

The advent of glass filament reinforced pipes was a significant advancein the solution of the problem of containing corrosive fluids atelevated pressures. The glass filaments were laid in the cylindricalwall of the pipe in a manner to resist tension and the normal lines ofstress in a pressurized cylinder. Furthermore, the thermoscttingresin-binder materials are capable of withstanding the corrosive actionof a wide variety of chemicals. Moreover, the glass-reinforced,resin-bound pipe has additional advantage over metal pipe in that it hasa higher specific strength, substantially higher corrosion resistanceand lower relative cost. In addition, it has a higher degree ofreliability not only in the pipe itself, but in the joints as well.

There are a number of commercially available methods of producingfilament wound pipe. However, each of the presently available methodsand apparatus is only capable of producing discrete, relatively shortsections of pipe. These processes are necessarily costly and involve agreat deal of labor cost as well as production time for producingfixed-length sections of pipe. There are a few presently availabledevices and methods for making continuous pipe, but all of these methodssuffer some very serious drawbacks. One of these methods employs acontinually moving mandrel where succeeding sections of mandrel areattached in endwise abutment and continually fed through a machine wherefilament is wound thereon. However, the various mandrel sections must beseparated so that the cured laminate can be cut into individual sectionsand removed from the mandrel sections. In another method of producingcontinuous pipe, an endless metal belt forms a mandrel by twisting thesame in'a spiral-like configuration so that it resembles the shape of acured pipe. Thereafter, the filament is wound upon this temporaryspiral-like mandrel. However, this device has not proved to beparticularly successful. Furthermore, it is quite costly to operate andrather inefficient.

The widespread acceptance of tubular members formed ofreinforced-plastics has occurred in other industries as well. Ithas'recently been recognized that fiber-reinforced composites can beeffectively employed in the manufacture of structural members, such asladder rails and the like. However, structural members, unlike fluidcarrying pipes, do not necessarily have symmetrical cross sections. Thisis particularly true in the case of ladder rails for example. In themanufacture of ladder rails, it is necessary to have two relativelythickopposed. end walls connected by two relatively thin side walls. Otherstructural members, such as supporting posts which can be formed ofreinforced composites also find variability in their cross sections.However, there is no effective commercially available apparatus ormethod for forming tubular structural members of filament reinforcedcomposites.

There have been a number of attempts to produce continuous tubularstructures by winding resin impregnated filament on a fixed mandrel andcontinually pulling the filamently wound structure through a curingdevice. However, these various attempts have been relativelyunsuccessful. The major drawback resides in the curing of the filament.These various prior art attempts employed various curing devices, whichby their nature, required fairly long cure time. The curing rate usuallydepended upon the thermal conductivity of the material and its abilityto conduct heat and initiate exothermic reactions. If the tubularstructure has any substantial wall thickness, thermal conductivity fromthe exterior surface to the interior surface of the tubular tially noway for the volatile materials in the resin to escape. Accordingly,cracks or fissures are often produced which results in the discarding ofthe product.

There have been a number of attempts to overwind extruded pipe andsimilar tubular structures where the tubular structure serves as a typeof in-situ mandrel. However, the same problems result from theineffective techniques for curing the resin-reinforcement matrix afterit is applied to the tubular structure.

OBJECTS It is, therefore, the primary object of the present invention toprovide an apparatus and method for producing continuously formedfilament reinforced tubes.

It is another object of the present invention to provide a method andapparatus of the type stated which employs a fixed metal mandrel forreceiving the wound strands of filament and which are ultimately curedand removed from the mandrel in a continuous process.

It is a further object of the present invention to provide an apparatusand method of the type stated which is readily and convenientlyadaptable to produce pipe of a wide variety of sizes and shapes.

It is another salient object of the present invention to provide anapparatus and method of the type stated which eliminates the costly needfor a large inventory of mandrels.

It is also an object of the present invention to produce a highperformance filament reinforced pipe which is capable of conductingcorrosive liquids at high flow rates, and which is capable ofwithstanding high internal pressures.

It is an additional object of the present invention to provide anapparatus and method of the type stated which is mounted upon a movingvehicle for continuously depositing pipe from the vehicle duringmovement thereof.

It is yet another object of the present invention to provide a methodand apparatus of the type stated which is capable of making reinforcedarticles having noncircular cross-sectional shapes, and which articlesare capable of being used in the manufacture of structural members. I

With the above and other objects in view, our invention resides in thenovel features of form, construction, arrangement and combination ofparts presently-described and pointed out.

FIGURES In the accompanying drawings FIG. 1 is a schematic sideelevational view, partially broken away and in section, of a tubeproducing apparatus for producing filament reinforced tube of thepresent invention;

FIG. 2 is a vertical sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is a fragmentary sectional view taken along line 3-3 of FIG. 1,showing a portion of the R-F curer of the present invention;

FIG. 4 is a fragmentary sectional view of a forced resin impregnatorforming part of the present invention;

FIG. 5 is a schematic side elevational view, partially broken away of aform of a tube producing apparatus constructed in accordance with thepresent invention and which employs resin impregnators as opposed to aresin tank;

FIG. 6 is a fragmentary sectional view of a modified form of resincontact impregnator used in the present invention;

FIG. 7 is a schematic side elevational view of another modified form oftube producing apparatus which employs an extruder producing tubingwhich in turn forms an in situ mandrel; 7

FIG. 8 is a vertical fragmentary sectional view taken along line 8-8 ofFIG. 7;

FIG. 9 is a schematic side elevational view, partially broken away andin section, of another modified form of tube producing apparatus whichforms a liner about which the filament reinforced strands are wound;

FIGS. 10 and 11 are vertical fragmentary sectional views taken alonglines 10-10 and 11-11 respectively of FIG. 9',

FIG. 12 is a schematic side elevational view, partially broken away andin section, of another modified form of tube producing apparatus whichemploys a mechanism for forming an in-situ type of mandrel fromsynthetic material and about which filament reinforced material can bewound;

FIG. 13 is a vertical fragmentary sectional view taken along line 13-13of FIG. 12;

FIG. 14 is a schematic side elevational view, partially broken away andin section, of another modified form of tube producing apparatus similarto the apparatus of FIG. 12, but does not form an in-situ mandrel;

FIG. 15 is a fragmentary sectional view taken along line 15-15 of FIG.14;

FIG. 16 is a schematic side elevational view of a modified form of tubeproducing apparatus which forms an in-situ liner by filamentwindingtechniques and which liners thereafter serve as an in-situ mandrel.

FIG. 17 is'a schematic side elevational view showing the employment of atube producing apparatus of the present invention for producingsubaqueous continuously formed filament reinforced pipe on a boat andlaying the same in a body of water;

FIG. 18 is a schematic side elevational view, partially broken away andin section, of a tube producing apparatus of the present invention forproducing tubular structural shapes;

FIGS. '19-21'are vertical sectional views taken along lines 19-19, 20-20and 21-21, respectively, of FIG. 18 showing the various steps in theformation of the ladder rails of the present invention, of which;

FIG. 19 shows the application of the longitudinal strands to the cornerof the mandrel;

FIG. 20 illustrates the longitudinal strands on the corners of themandrel with circumferential strands thereabout; v

FIG. 21 illustrates the final structure after all strands have beenapplied; I

FIG. 22 is a vertical sectional view taken along line 22-22 of FIG. 18and showing a portion of the shaping mechanism forming part of theapparatus;

FIG. 23 is a vertical sectional view taken along line 23-23 of FIG. 18and showing the portion of the curing mechanism of the apparatus;

I FIG. 24 isa schematic side elevational view of another modified formof tube producing apparatus of the present invention which employs anoverhead supply of longitudinal strands spools;

FIG. 25 is a fragmentary vertical sectional view taken along line 25-25of FIG. 24;

FIGS. 26A and B are schematic composite side elevational views of afurther modified form of tube producing apparatus which employs apultrusion machine producing tubing which in turn forms an in-situmandrel for further winding thereon;

FIG. 27 is a perspective view of a modified form of RF curer which canbe used in the apparatus of the present invention;

FIG. 28 is a horizontal sectional view taken along line 28-28 of FIG. 27and which shows the force field created by the R-F curer in dottedlines;

FIG. 29 is a perspective view of another modified form of R-F curerwhich can be used in the apparatus of the present invention;

FIG. 30 is a vertical sectional view taken along line 30-30 of FIG. 29and showing the force field created by the R-F curer;

FIG. 31 is a further modified form of R-F curer which can be employedwith the apparatus of the present invention;

FIG. 32 is a schematic perspective view of a microwave curing devicewhich can be used with the apparatus of the present invention;

FIG. 33 is a perspective view of a modified form of microwave curingdevice which can be used with the apparatus of the present invention;

FIG. 34 is a photomicrograph of 20 X magnification showing a portion ofa reinforced plastic composite which has been cured by a conventionalinductive heater;

FIG. 35 is a photo nicrograph of 5 0 X magnification showing a portionof the reinforced plastic composite of FIG. 34;

FIG. 36 is a photomicrograph of 20 X magnification show ing aportidifdfinofir reinforced plastic composite which has been cured byinductive heating;

16- 3 1 a shqtgm q sstaphsf q X ma fi of the reinforced plasticcomposite of FIG. 36;

FIG. 38 is a photomicrograph of 20 nggni fica tion showing a pbrtion ofa reinfor c plastic composite which has been cured by an R-F curing unitof the type used in the present invention; and M FIG 39 is aphotomicrograph of 50 X magnification showing a portion of thereinforced plastic composite Of FIG. 38.

DEFINITIONS Many of the terms employed in the filament winding art suchas spiral and helical have been used to describe a variety of situationsand consequently have no specific or definite meaning as such.Therefore, in order to ascribe a definite meaning to these terms for thepurposes of this application, the following definitions have been setforth:

Longitudinal A ply of one or more strands arranged substantially axiallywith a mandrel and generally parallel to the central axis of themandrel. A longitudinal ply should not deviate by more than a angle fromthe axial center line of the mandrel; the primary criterion being thatthis strand satisfies the demand of axial tension. Helical A ply of oneor more strands wrapped about Circumferential A ply of one or morestrands arranged circumferentially about the mandrel and has an anglewith respect to the axial centerline of the mandrel approximately from85 to 95; the primary criterion being that these strands satisfy a typeof burst load demand.

Spiral A ply of one or more helical strands applied in a form where theband width has a fixed relationship to the helical angle and mandreldiameter such that a continuous solid pattern results where arranged soeach of the strands lie side by side in an abutting relationship. (Mostof the helical windings in the present invention are in the form ofspiral windings; however the term helical as used in this applicationwill include spiral as well.)

Theangles for these above four types of wraps are not necessarilycritical as such, and are only set forth in order to define the type ofwrap which is being applied. In general, however, where the wrap or plyis de signed to provide high burst strength, the wrap is generally acircumferential wrap. Where the wrap or ply is designed to providecomponent forces to high axial and tensile loads, the wrap or ply isgenerally a helical wrap. Where the wrap or ply is designed to providehigh axial loads, the wrap is generally a longitudinal wrap.

The following terms have also been used with meanings of some vaguenessand therefore the following definitions are employed:

a mandrel so that it circumscribes the axial center- Filament Anindividual fiber generally for purposes of reinforcement, such. asglass, boron, graphite, etc.

End A group of filaments gathered in the form of a strand, where each ofthe filaments is essentially placed in parallel disposition and forms asubstantially planar band, the number of filaments depending upon thematerial employed. (In normal E iiberglass, 204 filaments are employedin an end.)

' Roving One or more ends arranged normally in a relatively thin fiatband. For normal E glass, the

r v roving illhave ogends, such as a 60-end roving.

Strand (band) One or more toil ings arafigeainesentially paralleldisposition to form a thin flat band.

GENERAL DESCRIPTION The present invention relates to a method and appa-1 ratus for the production of filament reinforced tubular members on acontinuous basis having both circular and noricircular cross-sections.The apparatus generally comprises a creel having a plurality of rovingspools for providing individual longitudinal filament strands. Thestrands are passedthrou'gh eyelets on the creel and into a resin ormatrix tank containing a matrix-curable material. The resinous materialimpregnates the strands of filament for ultimate cure in a manner to behereinafter described in detail. After the individual strands have beenimpregnated, they are passed forward and between a plurality of windingstations.

The device comprises a plurality of circumferential or helical windingstations which generally include a rotating disc. Filament spools aremounted upon oppositely presented flat surfaces of the disc and the discis rotated by means of a power source during the winding operation. An Aframe supports a trunnion-fixed mandrel in a substantially cantileverposition. The strands which pass from the resin tank are disposedlongitudinally along the-mandrel.

In the production of filament reinforced tubes, a plurality of firsthelical strands are wound upon the longitudinal strands at the firstwinding station. Thereafter, a plurality of helical strands which arereversed to the helix of the first winding station are wound about thetube being formed at the second winding station. This triad oflongitudinal strand additions and the helical winding stations may berepeated in order to form a tube with a desired wall thickness.Reversely located circumferential strands may be wound upon the formedtube at the final two winding stations. It is possible to provide anynumber of winding stations desired and to apply the desired type of wrapat each of these winding stations. In addition, it is possible to applylongitudinal strands at points disposed between one or more of thesewinding station's.

The tube which is being formed on the fixed mandrel extends into adielectric curing unit where the matrix is hardened. Thereafter, thetube extends outwardly of the curing unit and into a pulling unit. Thepulling unit is designed to continuously pull the tube off of the fixedmandrel as the tube is being formed thereon. In some applications ofusing the tubing where the tubing is being payed out at a controlledrate of speed it may be desirable to employ a braking unit which isdesigned to control the speed of dispensing the continuously formedtube. This tubing which can be formed of desired wall thickness isgenerally adaptable for use as pipe for transporting fluid. Byregulating the location and type of winding stations which are employedin the apparatus, it is possible to produce high pressure pipeadditional modification, the liner may not necessarily be cured, but maybe sealed along its longitudinal margins. In the case where the liner isnot sealedand cured, it is necessary to employ a fixed-mandrel whichextends at least into the curing unit.

In another preferred embodiment of the present invention, a fixedmandrel which is rectangular in crosssection is employed. On this typeof mandrel, it is possible to form ladder rails which are used in theconstruction of ladders. In the manufacture of rectangular ladder rails,it is desirable to provide relatively thick opposed end walls connectedby substantially thinner side walls. The apparatus of the presentinvention readily lends itself to the production of other structuralmembers.

Finally, the present invention provides an embodiment where aconventional pultrusion machine of the type described in US. Pat. No.2,871,911 produces a tubular member which serves as a subsequent in-situmandrel. Filament strands are applied to this tubular structure andsubsequently resin impregnated and finally cured. Again, there is noneed to employ a fixed mandrel where the pultrusion apparatus providesthe or low pressure pipe, or more specifically, pipe of the windingapparatus which employs a forced resin impregnator an opposed to a resintank. in thefor ced resin impregnator, the formed tube ispassed througha sleeve which contains a series of sonic drivers. The resin isintroduced into the interior of the sleeve and is urged into thewindings forming the-tube by means of the sonic drivers. As anotherembodiment in the present invention, a contact resin impregnator isemployed. In this case, the resin is merely introduced to the surface ofthe windings on the tube wall and is allowed to soak into the windings.Inflatable air seals may be used on the ends of each of the sleeves. Thepresent invention provides an apparatus which employs either of theseimpregnators as opposed to the resin tank. These impregnators may belocated after each of the winding stations or selectively after a numberof winding stations as desired.

The present invention also contemplates a continuous tube formingmachine which includes an extruder. The extruder is designed to extrudepipe or tubing which would serve as a liner about which filamentreinforced strands can be wound. Furthermore, there is no need to employa fixed mandrel in this type of apparatus inasmuch as the extruderprovides a fairly rigid tube which, in essence, serves as an in-situmandrel.

As another modification of the present invention, an apparatus isprovided which forms a liner of a synthetic resinous material about afixed mandrel. Thereafter, the desired number of winding stations may beemployed in order to wrap the strands of filament reinforced materialabout the liner. As another modification, the liner can be resinimpregnated and hardened so that it in essence serves as an in-situmandrel. As an in-situ structure for further winding thereon.

The present invention also provides an embodiment where any. of theaforementioned tube forming apparatus may be mounted on a moving vehiclesuch as a boat. As the tube is formed on the boat, it can becontinuously laid as the. boat moves. In the case of a land vehicle, thevehicle would be moved at the speed which is commensuratewith the rateof production of the pipe so that the pipe or tube, which may serve aspipe, can be continuously paid out. In the case of a boat, the pipe iscontinuously and subaqueously dispensed during the movement of the boat.

In any of the aforesaid apparatus, a dielectric curing unit of thetypeto be hereinafter described in more detail is employed. One of theunique aspects of each of the aforesaid embodiments of the presentinvention resides in the use of a dielectric curing unit for curing theresin matrix which is impregnated in the fiberglass strands. Theemployment of the dielectric heater enables the achieving of a tubularstructure with a wall thickness which is not economically feasible toachieve by other curing techniques. Even more importantly, thedielectric curing in each of the aforesaid apparatus enables theproduction of tubular structures with a quality whichalso could not beachieved by other types of curing techniques.

When the resin impregnated fiberglass is applied directly to a fixedmandrel without the aid of an in-situ liner, the frictional effectsresulting from the resin fiberglass composite is quite substantial andaccordingly,

ing mechanism employed in each of the apparatus of the present inventionalso enables a quick cure time and a highly quality end product.

The present invention contemplates both radio frequency (R-F) curing andmicrowave curing which comprise the dielectric curing unit in any of theaforesaid apparatus. A number of R-F energy applicator types aredisclosed as well as a number of microwave energy applicators.

DETAILED DESCRIPTXON Apparatus for Producing Reinforced Pipe Referringnow in more detail and by reference characters to the drawings whichillustrate practical embodiments of the present invention, A designatesan apparatus for producing high performance continuously wound filamentreinforced pipe. The apparatus A, can be mounted on a vehicle so that itis essentially mobile and utilized for operation from the bed of awheeled vehicle, floating vessel, sled, or other movable vehicle. Inaddition, the apparatus A is capable of being mounted in a stationaryposition and furthermore operated in either a vertical or horizontalposition or any desired attitude.

The apparatus A, generally comprises a base plate 1 and mounted upon oneend thereof is a spool rack 2 having a series of transversely extendingspindles 3 for accommodating conventional spools of filament or socalledroving 4. A separate eyelet is provided for each of the spools 4 and thestrands of filament 6 from each of the spools 4 are trained through theeyelet 5 associated with each spool.

Any continuous filament capable of being bent to conform to thecylindrical surface of a geometrically cylindrical body of revolutioncan be employed in the present invention. The most preferred filamentemployed in the present invention is that made of glass. However, itshould be recognized that filaments formed of carbon, quartz, graphite,asbestos, aluminum, etc. can be effectively used. Filaments formed oflithium and other grown-whisker crystals can also be employed. Inaddition, metal wire may be interspersed with the glass filaments in theevent that it is desired to add some type of metallic body to thefiberglass reinforced pipe which is produced, such as for electricalconductivity.

The various strands 6 of each of the filament spools 4 are passed over aroller 7 which is mounted on a resin tank 8, the latter being secured tothe base plate lin the manner as illustrated in FIG. 1. The variousstrands 6 are transversely spaced across the roller 7 and are passedinto a trough 9 forming part of the tank 8 and which contains a liquidresin. Furthermore, the strands are retained in the liquid resin bath bymeans of a holddown roller 10. At the opposite end of the tank, thestrands are held into the liquid bath by means of a hold- The matrixshould also possess the ability to adhere to the reinforcement. Someexamples of the suitable binders or matrix which can be employed in thepresent invention are various thermoplastic resins, such as nylon,polyethylene, polypropylene, many of the polycarbonates, polyesters,etc. In addition, thermosetting resins such as polyesters, many of thephenolics and epoxy etc. can be used. Generally, the thermosettingresins should be capable of being fused into an insoluble, nonheatsoftening mass upon application of heat or similar method of triggeringthe catalytic system. Other binders or matricesare hard waxes, eutecticceramics, eutectic metals, synthetic rubbers, etc.

Rigidly mounted on the base plate 1 and being longitudinally spaced fromthe resin tank 8 is an upstanding stand 13 having a trunnion 13' forsupporting a forwardly extending mandrel 14 in a cantilever position,reference being made to FIG. 1. Also mounted on the base plate 1 arefour longitudinally spaced inverted U shaped filament supportingbrackets 15 for carrying longitudinal strands of the filament after theyleave the resin tank 8. The U-shaped support brackets 15 are providedwith four substantially circumferentially spaced eyelets 16 foraccommodating the longitudinal strands of roving, for a purpose to bemore fully described in detail hereinafter.

Also mounted on the base plate 1 are four longitudinally spaced spoolsupport frames l7, 18, 19 and 20. Each of the spool frames 17-20 housesa circular spool support plate 21 and which is rotatable by means ofconventional electric motors 21 through a gear driven system (notshown). In essence, the spool support wheels may be provided with aperipheral pinion gear down roller 11. Thereafter, the strands are movedupwardly from the liquid resin bath and over a transversely extendingroller 12, similar to the roller 7. A pair of squeeze rollers couldoptionally be employed. The resin tank 8 is conventional in itsconstruction and therefore the details of construction of this tank arenot which can conventionally match with a spur gear mounted -'on thedrive shaft of the motor 21'. A sprocket and chain type drive may alsobe employed. Inasmuch as this type of drive is conventional, it isneither further illustrated nor described in detail herein.

Rotatably mounted on each of the spool support plates 21 and extendingoutwardly from both of the planar surfaces thereof are spindles 22 forsupporting conventional spools of roving 22', which are substantiallyidentical to the spools of roving 4. Furthermore, each of the plates 21is designed to carry fourto ten circumferentially spaced spools on eachof the planar surfaces or a total of eight to 20 spools on each plate.The terminal ends of the roving are threaded through eyelets orso-called redirects to a final placement eye (not shown) and which maybe supported on any conventional structure.

It should be recognized that it is not necessary to provide the mandrel14 with any coating. In the case of the present invention, it has beenfound that a highly polished chrome surface mandrel is also veryeffective. With many fibers, it is not at all necessary to even polishthe mandrel. It may also be desirable to form the mandrel with a veryslight taper so that the free end of the mandrel is slightly diametrallysmaller than the supported end thereof. The taper should end at thepointwhere the mandrel enters the curing zone, hereinafter described.- Thistaper on the mandrel will serve to relieve any constriction of thestrands which are wound thereupon.

By further reference to FIG. 1, it can be seen that the upstandingframes 17 and 18 constitute first right and left hand helical wrapstations W and W respectively. The support frames 19 and 20 with thewinding spools thereon constitute circumferential winding stations W andW respectively.

The mandrel id is the inner-surface-defining and major support elementfor producing the continuous pipe of the present invention. it can bemade from any suitable material capable of withstanding axial pullexperienced during the operation and the abrasion sustained by thescrubbing action of the uncoated fiberglass reinforced elements movingalong the length thereof. The mandrel, or a particular section thereof,must also be compatible with curing media to be hereinafter defined andwith the method of curing employed for any particular product.Furthermore, the mandrel may be coated with a' suitable smooth surfacedexterior liner such as a tetrafluoroethylene polymer marketed under thetrade name Teflon or ceramic metals or so-called cermets such as highalumina/silica. it should be recognized that while the mandrel 14 iscircular in vertical cross section, the mandrel may be made of anydesired cross section in order to produce tubing of a particularcross-sectional shape.

The pipe of the present invention is produced by applying a series oflongitudinal strands to the mandrel 14 directly from the roller 12.These strands can be carried over an upstanding guide 23 which ismounted on the trunnion 13 in the manner as illustrated in FIG. l.Furthermore, the strands are trained through a locating plate orso-called carding plate 23' for proper location and placement on themandrel 14. The carding plate 23' is preferably in the form of a ringcircumferentially disposed about the mandrel l4 and has an aperture foreach longitudinal strand applied to the mandrel. The plate 23' may besupported by any convenv tional supporting structure (not shown). Thepurpose of these initial longitudinal strands is to prevent constrictionand binding to the mandrel any helical or circumferential strands whichare subsequently applied. In addition, the longitudinal strands serve aspulling elements capable of receiving the axial band when the tubularmember beingformed is pulled along the mandrel. These initiallongitudinal strands can be applied so that the latter windings of thecircumferential, helical and spiral type do not contact the exteriorsurface of the mandrel 14. Similarly, sufficient longitudinal strandscan be circumferentially disposed about the mandrel 14 so that theysubstantially envelop the latter.

Thereafter, at the first winding station, a series of helical windingsare wound upon the exterior surface of the initial longitudinal strands.It can be seen that the filament from each of the spools can be trainedthrough suitable eyelets or so-called redirects. A separate eyelet willbe provided for each spool of roving. At the second winding station W areversely wound helical wrap is applied to the exterior surface of thefirst helical wrap. At the third winding station W 21 firstcircumferential wrap is wound about the exterior surface of the helicalwrap. Following this, an additional layer of circumferential strands isapplied to the thus formed tube at the last winding station W.,. Thislast layer of strands is applied in a direction reversed to thedirection of the application of the circumferential strands at thestation W In the alternative, it can be seen that another layer oflongitudinal strands may be applied to the surface of the first helicalwrap prior to the application of the second helical wrap at the windingstation W It is to be noted that each of the strands from spools 22 oneach side of the plate 21 are applied to the mandrel M at the samepoint.

While the apparatus A, has been illustrated as having four windingstations W,-W it should be understood that any desired number of windingstations may be employed. For example, in the case where it is desiredto produce high pressure pipe, it may be desirable to employ six toeight or more winding stations. F urthermore, while the winding stationsW and W have been described as helical winding stations and the windingstations W and W have been described as circumferential windingstations, it should be understood that other types of windings could beobtained at these stations/For example, it may be desirable to employone station with a circumferential wrap, another station with a helicalwrap and a third station with a circumferential wrap, or any combinationof these three in various forms. Accordingly, the present invention isnot limited to any specific number of winding stations, and furthermore,is not limited to any desired form of wrap. In addition to this, itshould be recognized that longitudinal strands can be introduced intothe formed pipe between any one or more of the winding stations.However, for purposes of illustrating the present invention, it can beseen that longitudinal strands are introduced prior to the first windingstation and are also introduced at each of the subsequent windingstations, namely stations W W v In the most preferred embodiment ofwinding, it is desirable to initially apply a series of longitudinalstrands which substantially circumferentially envelop the mandrel.Thereafter, the first helical wrap is applied in one direction at afirst winding station and a second helical wrap is applied in a reversedirection and a second winding station. This triad of longitudinal andfirst and second helical strands may be repeated any number of times asdesired in order to build up the wall thickness of the tube to beformed. The circumferential winding stations are generally applied atthe very end of the apparatus. However, it may be desirable to addadditional circumferential windings at any stage during the windingprocess in order to build up the burst-strength of the tube wall.

In the production of high performance filament reinforced pipe, it is attimes only necessary to employ two winding stations in addition to thewrap of longitudinal strands. In the case of high performance pipe, theinnermost layer must consist of longitudinal strands which substantiallyenvelop the circular mandrel. The longitudinal strands generally liedirectly on the mandrel surface as the first structural layer. The firstlongitudinal layer of strands must lie parallel to the axis of themandrel and must be uniformly distributed about t ond winding station, asecond helical wrap is disposed" upon the surface of the first wrap andthis wrap is located at an angle of 45, but in opposite directions tothe first helical wrap. In addition, it is sometimes desirable, in thecase of suspended pipe. to insert another longitudinal wrap at a pointin between each of the two helical wrap stations. The type of pipeproduced by this wrapping pattern has been found to be very suitable foruse in high pressure operations. In high pressure pipe, additionallayers of circumferential strands may be added to cover the demand ofadditional burst strength.

By reference to FIGS. 1 and 3, it can be seen that the mandrel 14extends into a suitable dielectric curing device 24, which isoperatively mounted on a stand 25, the latter being rigidly secured tothe upper surface of the base plate 1. It is possible to use radiofrequency curing or microwave curing for the purposes of the presentinvention. One particular radio frequency or so-called R-F curing unitwhich can be used in the present invention employs a co-axial electrodesystem and is more fully illustrated in FIG. 3. In this curing unit, itcan be seen that the mandrel extends into the unit for the entireeffective length thereof. A short section of aluminum pipe 26 iscircumferentially disposed about the mandrel 14 in the manner asillustrated in FIG. 3 and provides an annulus 27 therebetween. Actually,the metallic mandrel serves as the one electrode and the aluminum pipeserves as the other electrode. By a suitable R-F generator (not shown)it is possible to attain the desired radio frequency existing in theannulus 27 and thereby cure the wrap of filament strands disposed uponthe mandrel 14. The exterior surface of the mandrel l4 and the interiorsurface of the aluminum pipe 26 may be provided with Teflon layers28,29, respectively as illustrated in FIG. 3. The present invention isnot limited to the particular R-F curer illustrated and described hereinbut could be any of the R-F or microwave curing units describedhereinafter in more detail. I

The curing unit 24 is designed to obtain softening or melting and foractivating the catalysis system in a thermosetting resin. While theprior art has taught of various types of curing systems forthermosetting resins,

such as infrared heaters, induction heaters, forced air or gas heaters,etc., these systems have been found to be relatively ineffective in theapparatus of the present invention. However, it has been found thatdielectric 1 heating with a proper resin system is far more advantageousfor the purposes of the present invention, since these units are capableof curing the resin in the formed tubular member in a very short timeperiod and of enabling the production of a high quality product.Therefore, the problem of removing the pipe from the mandrel has beensubstantially eliminated. It is not effectively possible to employheated air or gas or infrared heating with the systems of the presentinvention since many of the composites are, in essence, thermallyins'ulative and will only effectively cure with R-F or microwave curingsystems.

The cured pipe is continuously pulled from the mandrel 14 by means of apulling unit 31, which is schematically illustrated in FIG. 1. Thepulling unit 31 is conventionally mounted upon a stand 32, the latterbeing secured to the base plate 1. The pulling unit 31 comprises a pairof continuous belts 32, which are operatively mounted on drive rollers33, and are disposed on opposite sides of the pipe which is thus formed.The pulling unit 31 must necessarily have sufficient pulling force toovercome the friction of the pipe on the mandrel 14. However, since theamount of space required due to the uniqueness of the heating and of thecloseness obtained in the various winding stations, the length of themandrel is not unduly long. Furthermore, the resin itself provides atype of lubricating activity so that the pipe, which is thus formed onthe mandrel 14 and cured in the curing unit 24, can be easily removedfrom the mandrel 14 by means of the pulling unit 31.

Resin Impregnators It is possible to eliminate the resin tank 8 andsubstitute therefor resin impregnators of the type illustrated in FIGS.4 and 6, and which are more fully illustrated and described in copendingapplication Ser. No. 723,554, filed Apr. 23, 1968. Referring to FIG. 4,R, designates a forced resin impregnator generally comprising an openended tubular housing or so-called canister 35 which is circular invertical cross section and includes a relatively thick annular wall 36having a central bore 37. The annular wall 36 is provided with a seriesof axially spaced circumferentially disposed circular plates 38 whichserve as force transducers or socalled sonic drivers. Each-of the plates38 are in turn connected to a suitable sonic energy generator forgenerating the necessary energy to drive the resin into the tubularmember passing into the housing 35.

As used herein, the term sonic is not limited to that energy sourcewhich is within the normal hearing range, namely 16 cycles per second to16 kilocycles per second. The term sonic also includes the subsonicrange which is approximately 0 to 16 cycles per second, the ultrasonicrange which is approximately 17 kilocycles per second to 780 kilocyclesper second and the hypersonic range which is approximately one megacycleper second to 15 megacycles per second, as well as the sonic range.

At each transverseend, the interior surface of the an-- nular wall 36 isprovided with a neoprene rubber seal 39 having an internal diameterwhich is sufficient to en- -able a filament wound tube to passtherethrough. By

reference to FIG. 4, it can be seen that the seals 39 are sized toaccommodate the tube as it passes through the housing 35. Furthermore,the seals 39 are sufficiently flexible to yield in order to accommodatenonlinearities in the circular dimension of the tube passing through thehousing 35. The seals 39 are also sufficiently rigid to maintain asubstantially fluid tight engagement betweenthe surface of the tube andthe interior of the housing 35. While the distance existing between theexterior surface of the tube and the interior surface of the annularwall 36 has been illustrated as being rather large, this illustration isonly for purposes of describing the present invention. However, itshould be recognized that this annulus has a substantially smallthickness and that the exterior surface of the tube is only veryslightly spaced from the interior surface of the wall The housing 35 isalso provided with a fitting 40 and a tube 40 connected to a suitablesource of liquid resin (not shown). In this matter, it is possible tocontinually supply a resin matrix to the housing 35. In like manner, thehousing 35 is also provided with an upwardly extending hollow standpipe41 which serves as an air accumulator. The standpipe 41 is provided witha removable cap 41 and a sight glass 42 which extends for the greaterportion of the vertical length of the standpipe 41. Air which has beenentrained in the various strands of the filament will be displaced bythe liquid resin as the strands enter into the housing 35. This air willbe

1. The method of producing filament reinforced tubular members on acontinuous basis and which tubular members have a continuous closed wallwith an inner wall surface and an outer wall surface, said methodcomprising the steps of impregnating filament containing strands with aresin matrix curable material having a high electrical loss tangent inthe monomeric form and a low electrical loss tangent in the polymericform, disposing said strands substantially longitudinally on a fixednon-movable mandrel having the overall shape of the desired finaltubular member, wrapping a first layer of filament containing strandsupon said longitudinal strands, wrapping a second layer of filamentcontaining strands over the first layer of strands, moving saidimpregnated strands in the form of said continuous closed wall on thefixed mandrel into a dielectric matrix material curing device, curingsaid matrix material impregnated into said strands with dielectricenergy within the frequency range selected from the class consisting of13 megahertz to 100 megahertz and 1500 megahertz to 25,000 megahertz sothat the innermost portions of the closed wall initially reaches ahigher temperature than the remainder thereof, permitting said member tocure exothermically initially from the center of the closed wall andprogressively outwardly to form a hardened tubular member, and removingsaid hardened tubular member from the mandrel.
 2. The method of claim 1further characterized in that the method includes the step of wrapping aplastic element about said mandrel, and applying said longitudinallydisposed strands to said plastic element.
 3. The method of claim 1further characterized in that the method includes the step of wrapping aplastic element about said mandrel, sealing the margins of said elementso that said element substantially envelops a portion of said mandrel,and applying said longitudinally disposed strands to said plasticelement.
 4. The method of claim 1 further characterized in that saidmember is continuously deposited from a moving vehicle as it isproduced.
 5. The method of claim 1 further characterized in that saidmember is continuously deposited subaqueously from a moving vehicle asit is produced.
 6. The method of producing filament reinforced tubularmembers on a continuous basis and which tubular members have acontinuous closed wall with an inner wall surface and an outer wallsurface, said method comprising the steps of forming a substantiallyrigid in-situ tubular element having the overall shape of the desiredfinal tubular member, impregnating filament containing strands with aresin matrix curable material having a high electrical loss tangent inthe monomeric form and a low electrical loss tangent in the polymericform, disposing said strands on the tubular element, moving said tubularelement with the strands thereon in the form of said continuous closedwall into a dielectric matrix material curing device, curing the matrixmaterial impregnated into said strands with dielectric energy within thefrequency range selected from the class consisting of 13 megahertz to100 megahertz and 1500 megahertz to 25,000 megahertz so that theinnermost portions of the closed wall initially reaches a highertemperature than the remainder thereof, permitting said member to cureexothermically initially from the center of the closed wall andprogressively outward to form a hardened tubular member, and removingsaid hardened tubular member from the mandrel.
 7. The method of claim 6further characterized in that the forming of the tubular elementcomprises extruding the tubular element in a rigid forM.
 8. The methodof claim 6 further characterized in that the forming of the tubularelement comprises the steps of wrapping a curable flexible film on afixed mandrel, and curing said film to form a substantially rigidtubular element.
 9. The method of claim 6 further characterized in thatthe forming of the tubular element comprises the steps of impregnatingfilament containing strands with a matrix curable material, applyingsaid impregnated strands to a fixed mandrel in a desired pattern, curingthe matrix material impregnated into said strands in a matrix materialcuring device to form the substantially rigid tubular element, andremoving the tubular element from the fixed mandrel.
 10. The method ofproducing filament reinforced tubular members on a continuous basis andwhich tubular members have a continuous closed wall with an inner wallsurface and an outer wall surface, said method comprising the steps ofimpregnating filament containing strands with a curable thermosettingresin material having a high electrical loss tangent in the monomericform and a low electrical loss tangent in the polymeric form, disposingsaid strands substantially longitudinally on a fixed non-movable mandrelhaving the overall shape of the desired final tubular member, wrapping afirst layer of filament containing strands upon said longitudinalstrands, wrapping a second layer of filament containing strands over thefirst layer of strands, moving said impregnated strands on the fixedmandrel into a curing device operable with RF energy, curing the resinmaterial impregnated into said strands with RF energy at a frequencywithin the range of 13 megahertz to 100 megahertz to cause electricalinteraction between the molecules of the resin material, permittingsurface heat on said resin impregnated strands to dissipate so that theinnermost portion of the closed wall initially reaches a highertemperature than the remainder thereof, permitting said member to cureexothermically initially from the center of the closed wall andprogressively outwardly to form a hardened tubular member, and removingsaid member from the mandrel.
 11. The method of claim 10 furthercharacterized in that the method includes the step of wrapping a waterimpervious element about said mandrel, and applying said longitudinallydisposed strands to said plastic element.
 12. The method of claim 10further characterized in that the method includes the step of wrapping awater impervious element about said mandrel, sealing the margins of saidelement so that said element substantially envelops a portion of saidmandrel, and applying said longitudinally disposed strands to said waterimpervious element.
 13. The method of claim 10 further characterized inthat said member is continuously deposited from a moving vehicle as itis produced.
 14. The method of claim 10 further characterized in thatsaid member is continuously deposited subaqueously from a moving vehicleas it is produced.
 15. The method of producing filament reinforcedtubular members of non-circular cross-section, having at least a firstpair of relatively flat walls and a second pair of relatively flatangularly located walls, on a continuous basis, said method comprisingthe steps of contacting filament containing strands with a resin matrixcurable material having a high electrical loss tangent in the monomericform and a low electrical loss tangent in the polymeric form, disposingsaid strands substantially longitudinally on a fixed non-movable mandrelof non-circular cross-section with at least a pair of relatively flatangularly located walls and having the overall shape of the desiredfinal tubular member, locating a greater number of strands on one of therelatively flat walls of the mandrel than on the other one thereof,wrapping a first layer of filament containing strands upon saidlongitudinal strands, wrapping a second layer of filament containingstrands over the first layer of strands, moving said stranDs on thefixed mandrel into a dielectric matrix material curing device, curingthe resin matrix material impregnated into said strands with dielectricenergy within the frequency range selected from the class consisting of13 megahertz to 100 megahertz and 1500 megahertz to 25,000 megahertz sothat the innermost portions of each of the relatively flat wallsinitially reaches a higher temperature than the remainder thereof,permitting said member to cure exothermically initially from the centerof the relatively flat walls and progressively outwardly to form ahardened tubular member of non-circular cross-sectional shape, andremoving said hardened tubular member from the mandrel.
 16. The methodof producing filament reinforced tubular members on a continuous basisand which tubular members have a continuous closed wall with an innerwall surface and an outer wall surface, said method comprising the stepsof impregnating filament containing strands with a curable thermosettingresin material having a high electrical loss tangent in the monomericform and a low electrical loss tangent in the polymeric form, disposingsaid strands substantially longitudinally on a fixed non-movable mandrelhaving the overall shape of the desired final tubular member, wrapping afirst layer of filament containing strands upon said longitudinalstrands, wrapping a second layer of filament containing strands over thefirst layer of strands, moving said impregnated strands in the form ofsaid continuous closed wall on the fixed mandrel into a curing deviceoperable with microwave energy, curing the resin material impregnatedinto said strands with microwave energy at a frequency within the rangeof 1500 megahertz to 25,000 megahertz to cause electrical interactionbetween the molecules of the resin material, permitting surface heat onthe outer wall surface of said continuous closed wall to dissipate andin such manner that the innermost portion of the closed wall initiallyreaches a higher temperature than the remainder thereof, permitting saidmember to cure initially from the center of the closed wall andprogressively outwardly to form a hardened tubular member, and removingsaid member from the mandrel.
 17. The method of claim 16 furthercharacterized in that the method includes the step of wrapping a plasticelement about said mandrel, and applying the longitudinally disposedstrands to said plastic element.
 18. The method of claim 16 furthercharacterized in that the method includes the step of wrapping a waterimpervious element about said mandrel, sealing the margins of saidelement so that said element substantially envelops a portion of saidmandrel, and applying the longitudinally disposed strands to said waterimpervious element.
 19. The method of claim 16 further characterized inthat said member is continuously deposited from a moving vehicle as itis produced.
 20. The method of claim 16 further characterized in thatsaid member is continuously deposited subaqueously from a moving vehicleas it is produced.
 21. The method of producing filament reinforcedtubular members on a continuous basis which comprises the steps ofwrapping a curable flexible film on a fixed mandrel, curing said film tothereby form a substantially rigid in-situ tubular element having theoverall shape of the desired final tubular member, removing said tubularelement from the fixed mandrel, impregnating filament containing strandswith a resin matrix curable material having a high electrical losstangent in the monomeric form and a low electrical loss tangent in thepolymeric form, disposing said strands on the tubular element, movingsaid tubular element with the strands thereon into a dielectric matrixmaterial curing device, curing the resin material impregnated into saidstrands with dielectric energy so that the innermost portions of themember formed of the resin matrix impregnated strands initially reachesa higher temperature than the remainder therEof, and permitting saidmember to cure initially from the center of said member andprogressively outward to form a hardened tubular member.
 22. The methodof claim 21 further characterized in that said member is continuouslydeposited from a moving vehicle as it is produced.
 23. The method ofclaim 21 further characterized in that said member is continuouslydeposited subaqueously from a moving vehicle as it is produced.
 24. Themethod of producing filament reinforced tubular members on a continuousbasis which comprises the steps of impregnating filament containingstrands with a matrix curable material, applying said impregnatedstrands to a fixed mandrel in a desired pattern, curing the matrixcurable material impregnated into said strands in a matrix materialcuring device to thereby form a substantially rigid in-situ tubularelement having the overall shape of the desired final tubular member,removing said tubular element from the fixed mandrel, impregnatingadditional filament containing strands with a resin matrix curablematerial having a high electrical loss tangent in the monomeric form anda low electrical loss tangent in the polymeric form, disposing said lastnamed impregnated strands on the tubular element, moving said tubularelement with the strands thereon into a dielectric matrix materialcuring device, curing the matrix curable material impregnated into saidstrands with dielectric energy so that the innermost portions of themember formed of the resin matrix impregnated strands initially reachesa higher temperature than the remainder thereof, and permitting saidmember to cure initially from the center of said member andprogressively outward to form a hardened tubular member.
 25. The methodof claim 24 further characterized in that said member is continuouslydeposited from a moving vehicle as it is produced.
 26. The method ofclaim 24 further characterized in that said member is continuouslydeposited subaqueously from a moving vehicle as it is produced.